Myeloperoxidase-antineutrophil cytoplasmic antibody-associated glomerulonephritis superimposed on biopsy-proven diabetic nephrosclerosis.

We present a case of myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA)-associated glomerulonephritis with diabetic nephrosclerosis, diagnosed by serial renal biopsies within a short period. A 78-year-old man with renal insufficiency, who had been diagnosed with diabetic nephrosclerosis by renal biopsy 9 months earlier, was admitted to the hospital for dyspnea and rapid deterioration of renal function. The titer of serum MPO-ANCA was high, and the second renal biopsy confirmed the presence of necrotizing glomerulonephritis with crescents. Methylprednisolone pulse therapy followed by oral administration of prednisolone led to resolution of respiratory symptoms and reversal of MPO-ANCA. Renal function did not improve, however, necessitating hemodialysis. A review of the literature showed several cases of necrotizing glomerulonephritis superimposed on diabetic nephropathy but only a few reported cases of MPO-ANCA glomerulonephritis associated with diabetic nephrosclerosis. Diabetic patients who show rapid deterioration of renal function should undergo renal biopsy to determine the concomitant presence, if any, of other glomerular diseases and to prevent life-threatening systemic involvement.